Asbestos economic importance

Economically important metamorphic minerals such as serpentine can affect health. In the past few years, asbestos removal has had significant impact on the cost of operating schools and other public buildings, hi the confusion over illness associated with asbestos made from the amphibole mineral crocidolite, citizens demanded the removal of all asbestos, unaware that a less-hazardous form of asbestos, the serpentine mineral chrysotile, also was removed at great expense. 

Ca. 98% of the worldwide production of asbestos (3.110 t/a in 1993, see Table 5.2-4) is chry.sotile. The most important deposits are in Canada and the former States of the USSR with the largest amphibole asbestos deposit being in South Africa. The worldwide reserves have been estimated to be 100 to 150 lO t/a and should at current consumption levels (2 I O t/a in 1997) last for 50 to 75 years. The asbestos content of the stone from economically workable deposits is ca. 4 to 10% (Quebec, Urals), the minimum level for economic workability being ca. 3%. 

For production work, plastics are normally cut using circular, band, jig or fret saws of the type commonly used for cutting metals but, in some cases, conventional wood working blades can be used. As with all plastics cutting tools, it is important to keep saws sharp so that they will run cool, and where long runs are involved, carbide tipped teeth can prove more economical, or even essential in the case of glass or asbestos filled material. Opaque acrylic materials are also more abrasive than transparent or translucent versions and it is preferable to use tipped saws when these are being cut in any quantity. 

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